Presser device for sewing machines



Feb. 17, 1970 F. L. WALLING 3,495,560

' PRESSERDEVICE FOR SEWING MACHINES Filed Aug. 14, 1968 Fig. I

INVENTOIR. FICIHCIS L. Wallmg I BY wumsss: i v

Rim-J2 m amm AT NEY United States Patent 3,495,560 PRESSER DEVICE FORSEWING MACHINES Francis L. Walling, Red Bank, N.J., assiguor to TheSinger Company, New York, N.Y., a corporation of New Jersey Filed Aug.14, 1968, Ser. No. 752,665

Int. Cl. D05b 29/12 US. Cl. 112235 4 Claims ABSTRACT OF THE DISCLOSUREThe sewing head portion of a sewing machine is dis closed including apresser device organized so that the presser bar and main presser springwill not be moved by the ordinary operation of the work feedingmechanism. The presser foot is carried on the presser bar by means of acurved leaf spring which, in addition to reducing the inertia oftheparts of the presser device that move substantially perpendicularlyof the direction of work feed in response to operation of the workfeeding mechanism, gives rise to movement of the presser foot thereby inthe line of work feed which minimizes the frictional resistance whichthe presser foot imparts to transport of the work.

Background of the invention This invention relates to sewing machinepresser devices, and more particularly, to presser devices of the lowinertia type adapted to be engaged periodically with a sewing machinework feeding mechanism.

In sewing machines employing a drop feed mechanism, i.e., a work feedingmechanism including a feed dog which is raised above the level of a worksupporting throat plate and advanced, and then dropped beneath the levelof the throat plate and returned, a presser device serves to press theplies of fabric being seamed against the throat plate and in oppositionto the feed dog when it is raised. It has long been recognized in theart that inertia forces acting on the presser device can result in anupward overthrow of the presser foot after the rise of the feed dogresulting in failure of the presser device to oppose the feed dogconsistently during the work-advance stroke of the feed dog. A number oflow inertia presser devices are known in the art for minimizing suchinertia forces acting on the presser foot.

Perfection in the transport of work fabrics past the stitching point ofa sewing machine, however, involves considerations in addition to thatof consistently urging the work fabrics against the feed dog. There is,for instance, a profound difference between the factors which influencefeeding of a lower ply of fabric which directly engages the feed dog andthose factors which influence feeding of a top ply of fabric whichengages the presser foot. The production of fiat, wrinkle free seamsrequires, from the standpoint of work feeding, that the top and bottomplies of work fabric must be advanced in like amounts. The top ply offabric can, however, be retarded relatively to the bottom ply byfriction forces developed against the presser foot.

It is an object of this invention to provide a low inertia presserdevice for a sewing machine comprising an assembly of simple parts whichdo not require accurate tolerances therebetween.

Another object of this invention is to provide a presser device for asewing machine which coacts in a novel manner with a drop feed mechanismof a sewing machine to minimize the friction forces developed by the topply of work fabrics against the presser foot so that optimum uniformityof advance of top and bottom plies of work fabric can result.

3,495,566 Patented Feb. 17, 1970 Summary of the invention The objects ofthis invention are attained by means of a sewing machine presser devicein which the presser bar and the force of the main presser bar springwhich acts between the machine frame and the presser bar are limited asto movement toward the work support by a stop means. Interposed betweenthe presser bar and the presser foot is a U-shaped leaf spring of whichthe spaced horizontal limbs are secured one to the presser bar and theother to the'presser foot at points in substantial alignment with thelengthwise axis of the presser bar. Deformation of the leaf springduring rise of the feed dog causes the presser foot to move in thedirection of feed of the work fabrics, and therefore, transport of thework fabrics during advance of the feed dog is opposed by kineticfriction between the top ply and the presser device. The kineticfriction being of a lower value than the static friction which must beovercome when a conventional presser device is used, the retardation ofthe top ply by the presser foot is minimized with this invention andunformity of feed of the plies is enhanced.

Description of the drawings With the above and additional objects andadvantages in view as will hereinafter appear, this invention comprisesthe device, combinations, and arrangements of parts hereinafterdescribed and illustrated in the accompanying drawing of a preferredembodiment in which:

FIG. 1 represents a head end elevational view of a sewing machine partlyin cross section illustrating the presser device of this invention incooperation 'with a drop feed mechanism,

FIG. 2 is a disassembled perspective view of the presser foot and theauxiliary leaf spring support therefor, and

FIG. 3 is a fragmentary elevational view showing the presser foot withthe feed dog and illustrating in phantom lines the position to which thepresser foot moves in the direction of work feed during the rise of thefeed dog. For the purposes of illustration, the phantom line position issomewhat exaggerated.

Referring to the drawings, FIG. 1 illustrates portions of a sewingmachine as viewed from the head end and includes a sewing machine bed 11formed with an opening 12 covered by a throat plate 13 which is formedwith slots 14 upwardly through which operates a feed dog. The feed dog15 forms a part of a conventional drop feed mechanism for sewingmachines, which is also referred to in the art as a four-motion workfeeding mechanism. The feed dog is carried by a feed bar 16 pivoted asat 17 to a rock arm 18 on an oscillating feed advance shaft 19 whichimparts advance and return movements to the feed dog. At the oppositeextremity the feed bar is pivoted as at 20 to link 21 pivotallyconnected as at 22 to a rock arm 23 of an oscillating feed lift rockshaft 24 which imparts rising and falling motion to the feed dog. Thecombination of such advance and return movements together with therising and falling movements of the feed dog results in a path of motionof the feed dog in an oval shape as indicated at 25 in FIG. 3.

The throat plate 13 is also formed with an aperture (not shown) toaccommodate endwise reciprocation of a needle which is carried by aneedle bar 31 in bushings in a bracket arm 32 cantilevered over the bed11 as is conventional in sewing machine frame construction. Alsosupported in a bushing 33 in the bracket arm 32 for lengthwise slidingmovement therein is a presser bar 34. At the upper extremity,the presserbar is formed with an axial bore 35 which accommodates a locating pin 36formed between its ends with a flange 37 which abuts the upper extremityof the presser bar 34. The locating pin 36 above the flange 37 extendswithin the coils of a main presser spring 38 which also embraces alocating pin 39 depending from an adjusting screw 40 threaded into thebracket arm 32. Secured to the presser bar 34 as by a set screw 41 is acollar which may be formed with a lateral extension 43 slideablyconstrained against the bracket arm to prevent rotation of the presserbar. The collar 42 in the present invention serves in an additionalcapacity to limit downward movement of the presser bar 34 under theaction of the main presser spring 38. To this end a wire brackett 44 isformed with a loop 45 encircling the presser bar beneath the collar 42and with a loop 46 encircling a pin 47 projecting from a presser liftinglever 48 which is provided on a fulcrum screw 49 exteriorly of thebracket arm. Also pivoted exteriorly of the bracket arm on a fulcrumscrew 50 is a manual presser lifting bell crank 51 which abuts beneaththe presser lifting lever 48. When the bell crank 51 is turned to theposition as shown in FIG. 1 which the presser bar is lowered, the bellcrank 51 determines a stop position by way of the wire bracket 44dictating the lowest position in which the presser bar may move.

The lower extremity of the presser bar 34 is formed with a plaincylindrical portion above which the presser bar is formed with screwthreads 61 which accommodate a locking and adjusting nut 62. The presserdevice of this invention is secured to the lower extremity of thepresser bar by means of a split clamp 63 adapted to embrace the plaincylindrical portion 60 at the presser bar extremity and to be securedthereon by a clamp screw 64. The locking and adjusting nut 62 serves toprovide an adjustable abutment for locating the position of the splitclamp 63 accurately on the cylindrical portion of the split clamp 63accurately on the cylindrical portion '60 of the presser bar. The splitclamp 63 is formed with the threaded hole 65 which accommodates a headedfastening screw 66 which together with a washer 67 provide a fasteningmeans by which a first limb 68 of U- shaped leaf spring 69 may besecured to the presser bar. The first limb 68 of the leaf spring ispreferably formed with an open slot 70 to accommodate a fastening screw66 with provision for a limited adjustment of the leaf spring relativelyto the presser bar.

The leaf spring 69 is formed with a curved central portion 71 and with asecond limb 72 extending substantially parallel to the first lim-b 68.Secured to the second limb 72 of the leaf spring as by fastening screws73 and located between the spring limbs 68 and 72 is a block 74 which isformed with an upwardly open slot 75. The screws 73 pass throughclearance openings 76 in the second limb 72 of the leaf spring andthreadedly engage tapped holes 77 in a bearing block 78 beneath thesecond leaf spring limb 72. The fastening screw preferably orients theslot in the block 74 so that the slot extends toward the curved centralportion 71 of the leaf spring. The bearing block 78 is formed with atransverse bore 79 to accommodate a fulcrum pin 80 by whicha sewingmachine presser foot 81 is pivoted with respect to the presser bar. Thepresser foot is preferably formed with a pair of spaced projections 82,83, the projection 83 being formed with a clearance aperture 84 for thefulcrum pin and the projection 83 being formed with a tapped hole 85into which the threaded extremity of the fulcrum pin 80 engages.

The headed fastening screw 66 by which the leaf spring 69 is secured tothe presser bar is formed with a depending cylindrical extension whichis slideably accomodated within the slot 75 of the block 74 secured tothe second limb of the leaf spring. The cylindrical extension 90 and theslot 75 of the block 74 cooperate to provide a lateral guide means whichwill not inhibit limited vertical movement of the presser footrelatively to the presser bar, nor will it inhibit movement of thepresser foot in the direction of feed of the work relatively to thepresser bar.

Since downward movement of the presser bar 34 is limited by the stopmeans acting beneath the collar 42 on the presser foot bar, the pressureof the main presser spring 38 is prevented from acting directly on thepresser foot 81, and only the auxiliary leaf spring 69 acts to urge thepresser foot downwardly during the normal operation of the sewingmachine, that is, unless an extraordinarily thick cross seam or the likeis encountered. As a consequence during normal operation of the sewingmachine, only the presser foot, the blocks 78 and 74, and a portion ofthe spring 6 9 will move upwardly during the rise of the feed dog 15.Since the entire presser bar and main presser spring arrangement willnot move during normal sewing and since the parts which do move possesvery low mass, a minimum of inertia forces will be developed and thepresser foot will follow the movements of the feed dog with a minimum ofoverthrow.

In addition to following the movements of the feed dog closely whichwill produce optimum consistency of stitch length in the resulting feedof the work fabrics, the presser device of this invention also operatesin a unique fashion to minimize the drag of the presser device on thetop ply of Work fabrics being sewn so that optimum uniformity of feedbetween the upper and lower plies of work fabric being stitched will beprovided. The minimizing of drag exerted by the presser foot of thisinvention on the top ply of work pieces is believed to result from thefact that during the rise of the feed dog at the outset of each workfeeding stroke, the presser foot, in addition to being raised by thefeed dog, will also partake of an increment of movement in the directionof feed of the work. This increment of presser foot movement relativelyto the work will overcome the static friction which exists between thetop ply of work fabrics and the presser foot, so that as work isadvanced by the feed dog only the kinetic friction between the top plyand the presser foot will be effective. Since the kinetic coefficient offriction is of lower value than the static coeflicient of friction, suchinitial presser foot movement in the direction of feed at the outset ofeach feeding stroke is believed to account for the superior uniformityof feed of the plies of fabric which is the object of this invention.

Having set forth the nature of this invention, what is claimed hereinis:

1. A presser device for a sewing machine including a work support and apresser bar having a lengthwise axis extending substantiallyperpendicular to the work support in said sewing machine, said pressuredevice comprising a U-shaped leaf spring including spaced substantiallyparallel first and second limbs joined by a curved central portion ofsaid spring, fastening means for attaching the first limb of said leafspring to said presser bar in a position extending substantiallyperpendicular to the lengthwise axis of said presser bar, a presser footadapted for engagement with said work support, and securing means forattaching said presser foot to the second limb of said leaf spring.

2. A presser device as set forth in claim 1 in which said securing meansfor said presser foot engages said second limb of said leaf spring at adistance from said curved central portion thereof which is greater thanthe distance from said curved central portion to said fastening means onsaid first limb of said leaf spring.

3. A presser device as set forth in claim 1 in which said fasteningmeans includes a guide pin extending substantially parallel to thelengthwise axis of said presser bar, and in which said securing meansincludes a block formed with a guide pin embracing slot, said slotextending along said second limb of said leaf spring toward said curvedcentral portion thereof.

4. In combination with a sewing machine having a frame including anapertured work support, a drop feed mechanism inside said frameincluding a feed dog operating upwardly through said apertured worksupport, a

presser bar endwise slideably mounted in said frame above said worksupport, a main presser spring biasing said presser bar toward said worksupport, and stop means limiting movement of said presser bar towardsaid work support, a presser device carried by said pressed bar andincluding a leaf spring, fastening means securing a first extremity ofsaid leaf spring to said presser bar, a curved central portion formed onsaid leaf spring positioning a second extremity thereof in spacedrelation beneath and substantially perpendicular to said presser bar, apresser foot engageable with said work support and with said feed dogoperating therethrough, and securing means for attaching said presserfoot to said second extremity of said leaf spring.

References Cited UNITED STATES PATENTS 10 PATRICK D. LAWSON, PrimaryExaminer

